A roll leveller is a device for uncoiling and smoothing out coiled materials to be fed to a press. The most popular and effective method of supplying such coiled materials to a press is by the use of such a roll feeder.
Where the press is a transfer type press having a plurality of metal molds, the supplied material has to be aligned in the right position. Therefore, each metal mold is provided with a pilot punch which operates to lift the feed roll of a roll feeder slightly above the material being fed so as to allow free movement of the material for a predetermined period of time.
The above operation is called the releasing of the roll feeder and a releasing device which temporarily releases the contact of the feed roll with the material is provided for all types of roll feeders. Since the roll leveller is provided at a position close to the roll feeder, when the feed roll of the roll feeder is released, the work rolls of the roll leveller should also be released simultaneously in order to permit the material to move freely.
The work rollers of the prior art roll levellers are released by the operation of hydraulic cylinders provided for each roll of the groups of work rolls. Since the releasing movement of this type tends to take some time, it is difficult to increase the rate of operation of the press or the number of operations of the slide per unit time, thus making it difficult to increase productivity.